const boxes=document.querySelectorAll('.box');

window.addEventListener('scroll',()=>{
    const triggleBottom=window.innerHeight*4/5;
    boxes.forEach((item)=>{
        const boxTop=item.getBoundingClientRect().top;
        if(boxTop<triggleBottom){
            item.classList.add('show');
        }else{
            item.classList.remove('show');
        }
    })
})